System and method for adaptive network technique using isochronous transmission

ABSTRACT

A network including a plurality of nodes each configured as transmitters, receivers, or transceivers. At least one of the nodes may be configured to wirelessly transmit a repeating isochronous signal for reception by one or more of the other nodes. The isochronous phase and/or frequency of the repeating isochronous transmission may be variably adjusted to reduce signal interference.

RELATED APPLICATION

The present application is a continuation of, and claims prioritybenefit to, co-pending and commonly assigned U.S. patent applicationentitled “SYSTEM AND METHOD FOR ADAPTIVE NETWORK TECHNIQUE USINGISOCHRONOUS TRANSMISSION,” application Ser. No. 11/681,692, filed Mar.2, 2007, which claims the benefit of U.S. Provisional Application No.60/778,695, entitled “METHOD AND SYSTEM FOR ADAPTIVE NETWORK TECHNIQUEUSING ISOCHRONOUS TRANSMISSION,” filed Mar. 3, 2006, which are hereinincorporated by reference in their entirety.

BACKGROUND

1. Field

Embodiments of the present invention relate to adaptive networktechniques. More particularly, various embodiments of the inventionprovide methods and apparatuses operable to utilize isochronoustransmissions to communicate information between independent networknodes.

2. Description of the Related Art

Wireless communication methods may be employed to enable variousdiscrete devices to exchange information. For example, wireless devicesmay employ the Bluetooth or Zigbee (IEEE 802.15.4) specifications totransmit and receive information over short ranges. Unfortunately,wireless devices configured to employ Bluetooth, Zigbee, or otherwireless specifications and protocols often consume unsatisfactoryquantities of power and require relatively complex and expensivemicrocontrollers due to the complexities and demands of these variousspecifications and protocols. Consequently, battery powered devicesusing these protocols typically possess very poor battery life and arenot cost effective.

SUMMARY

Embodiments of the present invention solve the above-described problemsand provide a distinct advance in the art of adaptive networktechniques. More particularly, various embodiments of the inventionprovide methods and apparatuses operable to utilize isochronoustransmissions to communicate information between network nodes.

In various embodiments, the present invention provides a networkincluding a plurality of nodes each configured as transmitters,receivers, or transceivers. At least one of the nodes may be configuredto wirelessly transmit a repeating isochronous signal for reception byone or more of the other nodes. The isochronous phase and/or isochronousfrequency of the repeating isochronous transmission may be variablyadjusted to reduce signal interference. Nodes receiving the repeatingisochronous signal may identify its transmission characteristics, suchas its phase and frequency, and receive signals according to theidentified characteristics to enable low-power operation.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not necessarily restrictive of the invention claimed. Theaccompanying drawings, which are incorporated in and constitute a partof the specification, illustrate embodiments of the invention andtogether with the general description, serve to explain the principlesof the invention.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Various embodiments of the present invention are described in detailbelow with reference to the attached drawing figures, wherein:

FIG. 1 is a block diagram illustrating a plurality of network nodesconfigured in accordance with various embodiments of the presentinvention;

FIG. 2 is a block diagram illustrating some of the components of one ofthe nodes illustrated in FIG. 1;

FIG. 3 is a block diagram of an exemplary message format that may beemployed by the nodes of FIG. 1;

FIG. 4 is a signal diagram illustrating an exemplary transmission of arepeating isochronous signal by one of the nodes of FIG. 1;

FIG. 5 is a signal diagram illustrating an exemplary burst communicationemployed by two of the nodes of FIG. 1;

FIG. 6 is signal diagram illustrating another exemplary burstcommunication employed by two of the nodes of FIG. 1;

FIG. 7 is a signal diagram illustrating an exemplary burst transfer dataerror associated with a burst communication;

FIG. 8 is a signal diagram illustrating an exemplary burst transferrequest error associated with a burst communication; and

FIG. 9 is a signal diagram illustrating an exemplary channel searchingtechnique operable to be employed by one or more of the nodes of FIG. 1.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating various embodiments of the invention.

DETAILED DESCRIPTION

The following detailed description of various embodiments of theinvention references the accompanying drawings which illustrate specificembodiments in which the invention can be practiced. The embodiments areintended to describe aspects of the invention in sufficient detail toenable those skilled in the art to practice the invention. Otherembodiments can be utilized and changes can be made without departingfrom the scope of the present invention. The following detaileddescription is, therefore, not to be taken in a limiting sense. Thescope of the present invention is defined only by the appended claims,along with the full scope of equivalents to which such claims areentitled.

Various embodiments of the present invention provide a wireless network10 including a plurality of network nodes 12. One or more of the nodes12 may be configured to wirelessly transmit a repeating isochronoussignal for reception by one or more of the other nodes 12. Theisochronous phase and/or isochronous frequency of the repeatingisochronous transmission may be variably adjusted to reduce signalinterference.

In various embodiments as shown in FIG. 2, each node 12 may include atransceiver 14, a processing system 16 coupled with the transceiver 14,a clocking system 18 coupled with the transceiver 14 and/or processingsystem 16, and an input/output interface 20 coupled with the transceiver14 and/or processing system 16. The transceiver 14, processing system16, clocking system 18, and interface 20 may be disposed within a commonhousing or separately positioned within two or more housings.

The transceiver 14 may include any element or combination of elementsoperable to receive a transmitted signal for use by the processingsystem 16. In various embodiments, the transceiver 14 includes anantenna and associated signal processing circuitry to enable thetransceiver 14 to receive signals corresponding to desired frequencies.The transceiver 14 may be operable to be tuned to correspond toparticular transmission frequencies. For instance, the processing system16 may control the transceiver 14 to receive transmitted signals havinga desired frequency.

In some embodiments, the transceiver 14 may also include power controlcircuitry to enable the transceiver 14 to be easily activated anddeactivated. For example, the processing system 16 may be operable toprovide an activation signal to the transceiver 14 to activate thetransceiver 14 and provide a deactivation signal to the transceiver 14to deactivate the transceiver 14. When activated, the transceiver 14 isoperable to receive transmitted signals. When deactivated, thetransceiver 14 provides less than full functionality and may begenerally inoperable to receive transmitted signals. Consequently, thetransceiver 14 may be easily activated and deactivated to conserve nodepower when it is not necessary to receive a signal.

In some embodiments, the transceiver 14 may additionally oralternatively be operable to transmit signals, as is discussed in moredetail below. Thus, each one of the nodes 12 and its correspondingtransceiver 14 may be configured as a receiver operable to receivesignals, a transmitter operable to transmit signals, or a transceiveroperable to transmit and receive signals. The transceiver 14 may includediscrete receiving and transmitting elements such that it does notnecessarily form an integral unit. In some embodiments, the transceiver14 may be configured to dynamically switch between receiving andtransmitting functions to conserve power. For example, the processingsystem 16 may provide various control signals to the transceiver 14 toenable and disable receiving and transmitting functionality based on theneeds of one or more of the nodes 12.

The transceiver 14 may also be configured to receive more than onesignal simultaneously such as through the inclusion of a plurality ofreceiving elements. Additionally, the transceiver 14 may be configuredto transmit more than one signal simultaneously such as through theinclusion of a plurality of transmitting elements. Further, thetransceiver 14 may simultaneously transmit and receive a plurality ofsignals based on various control signals provided by the processingsystem 16.

The processing system 16 is coupled with the transceiver 14 and may begenerally operable to control the functionality of the transceiver 14and process signals acquired by the transceiver 14. The processingsystem 16 may include various analog and digital components operable toperform these and the various other functions discussed herein. In someembodiments, the processing system 16 may include a microprocessor, amicrocontroller, a programmable logic device, digital and analog logicdevices, computing elements such as personal computers, servers,portable computing devices, combinations thereof, and the like. Inembodiments where the nodes 12 are configured as low-power devices, theprocessing system 16 may be configured as a low-power programmable logicdevice, microcontroller, microprocessor, and the like.

The processing system 16 may also include, or be operable to couplewith, a memory 22. The memory 22 may include any computer-readablememory or combination of computer-readable memories operable to storedata for use by the processing system 16. For instance, the memory 22may be operable to store isochronous signal information, isochronousfrequency and phase information, information corresponding to receivedand transmitted signals, combinations thereof, and the like.

The processing system 16 may be discrete from the transceiver 14 andother elements discussed herein. However, in some embodiments, theprocessing system 16 may be integral with the transceiver 14. Forexample, a single integrated circuit may embody both the transceiver 14and processing system 16. Further, the functionality of the transceiver14 and processing system 16 may also be distributed between severalelements, such as between a plurality of integrated circuits or discretedigital and analog components. The processing system 16 may additionallyor alternatively be integral with the clocking system 18 or interface 20to reduce the physical size associated with each node 12.

The clocking system 18 is operable to couple with the transceiver 14and/or the processing system 16 to provide a clock signal thereto. Insome embodiments, the clocking system 18 may provide similar oridentical clock signals to both the transceiver 14 and processing system16 for use in various signal reception and processing functions.However, in other embodiments, the clocking system 18 may be operable toprovide dissimilar clock signals to the transceiver 14 and theprocessing system 16. For example, the clocking system 18 may provide afirst clock signal having a first rate to the processing system 16 and asecond clock signal having a second rate to the transceiver 14, wherethe second rate is greater than the first rate. The clocking system 18may also be operable to provide a plurality of different clock signals,each having a different rate, to portions of the processing system 16and transceiver 14. Such a configuration enables portions of each node12 to operate at high frequencies, such as those required to receiveand/or transmit high-frequency signals, while allowing other portions ofeach node 12, such as the processing system 16, to operate at lowerfrequencies and thereby conserve power.

In some embodiments, the clocking system 18 may include an independentclock for timing isochronous transmission periods. For example, as isdiscussed in more detail below, the transceiver 14, other clocks, andother portions of the node 12 may be deactivated to conserve power whenit is not necessary for the node 12 to transmit or receive signals. Theindependent clock may be a low-power element operable to activate atleast portions of the transceiver 14 and/or processing system 16 basedon one or more utilized isochronous transmission periods. Thus, when thenode 12 is not transmitting or receiving signals, only the independentclock may be active to ensure that the node 12 maintains proper timing.

The clocking system 18 may be discrete from the processing system 16 andtransceiver 14. However, in some embodiments, the clocking system 18 maybe integral with both the transceiver 14 and processing system 16, suchas where a first clock source is associated or integrated with theprocessing system 16 and a second clock source is associated orintegrated with the transceiver 14.

The clocking system 18 may comprise any elements or combination ofelements operable to generate one or more clock signals. The clockingsystem 18 may include a plurality of clock elements and systems. Invarious embodiments, the clocking system 18 includes a digitallycontrolled oscillator (DCO) to provide one or more clock signals to thevarious node elements. However, the clocking system 18 may additionallyor alternatively include other clock generating elements, such asconventional clocking circuits, crystal clock elements, physical clockelements, combinations thereof, and the like.

The interface 20 allows each node 12 to access various externalelements. For instance, in embodiments where the memory 22 is notintegral with the processing system 16, the interface 20 allows theprocessing system 16 and/or transceiver 14 to access the memory 22 toacquire and save data. For example, the interface 20 may include amemory card interface operable to couple with a flash memory card orother common memory elements. In embodiments where the memory 22 isassociated with a discrete computing device, the interface 20 allows theprocessing system to access the computing device and associated memory22.

The interface 20 may provide wired and/or wireless connections discretefrom the reception and transmission capabilities of the transceiver 14.Thus, in some embodiments the interface 20 may provide a serialinterface, such as a RS232 interface, a SPI interface, an I2C interface,a parallel interface, a wired network interface such as an Ethernetinterface, a USB interface, a cellular interface, a RFID interface, ashort-range wireless interface, combinations thereof, and the like.Thus, the interface 20 enables the processing system 16 to easilycommunicate with external computing, memory, and network devices andsystems to send and retrieve information for configuration andcommunication purposes.

In operation, the network 10 may be configured utilizing the variousnodes 12. For instance, one or more of the nodes 12 may be configured totransmit signals, one or more of the nodes 12 may be configured toreceive signals, and/or one or more of the nodes 12 may be configured toreceive and transmit signals. Each node 12 may provide received andtransmitted signals and any information associated therewith to variouscomputing devices, memories, and/or other systems and devices utilizingits respective interface 20.

In various embodiments, a first node 12 a may be configured to transmita repeating isochronous signal. The first node 12 a may be operable totransmit repeating isochronous signals according to one or moreisochronous phases and isochronous frequencies. “Isochronous signal,” asutilized herein, refers to a signal with an isochronous transmissionperiod that is not dependent upon a global or master synchronizingdevice. “Isochronous phase”, as utilized herein, refers to positioningof isochronous transmissions and receptions relative to otherisochronous transmissions and receptions, with a similar isochronousfrequency on the same node. “Isochronous frequency,” as utilized herein,refers to the rate at which a repeating isochronous signal istransmitted and not the frequency of the transmitted signal itself.

For example, the first node 12 a may transmit a first repeatingisochronous signal having an isochronous frequency of 8 Hz, where thecarrier frequency of the transmitted signal may itself be in the 2.4 GHzrange. The first node 12 a may in addition transmit a second isochronoussignal having an isochronous frequency of 8 Hz, where the secondisochronous transmission begins repeatedly 50 ms after the firstisochronous transmission, providing an isochronous phase difference of50 ms.

The repeating isochronous signals transmitted by the first node 12 a mayhave any isochronous transmission period, isochronous phase, isochronousfrequency, and/or other timing or synchronizing characteristics,regardless of the configuration of other devices or nodes 12 associatedwith the network 10. An exemplary repeating isochronous signal andcorresponding isochronous transmission period are illustrated in FIG. 4,where each “Master 1 Tx” indicates a transmission of the repeatingisochronous signal.

In some embodiments, the processing system 16 corresponding to the firstnode 12 a is operable to variably adjust a transmission characteristicof the repeating isochronous signal, such as the isochronous phaseand/or isochronous frequency of the repeating isochronous signal. Thus,the utilized isochronous phases and isochronous frequencies are notnecessarily static values and may be varied by any amount by the firstnode 12 a to achieve any desired effect, including limiting interferenceand increasing node interoperability.

The processing system 16 or memory 22 associated with the first node 12a may include a list or database of isochronous phases and isochronousfrequencies and the processing system 16 may select which isochronousphase and/or frequency to utilize for transmitting the repeatingisochronous signal. Utilizing the interface 20, a user may also selectwhich isochronous phase or isochronous frequency to utilize, such as byproviding an input or by storing information in the memory 22. In someembodiments, the first node 12 a may initially employ a defaultisochronous frequency and/or isochronous phase and modify the frequencyand/or phase as needed, as is discussed in more detail below. Theprocessing system 16 may also randomly select the isochronous phaseand/or frequency of the repeating isochronous signal for use intransmitting signals.

In various embodiments, the processing system 16 corresponding to thefirst node 12 a may variably adjust the isochronous frequency and/orisochronous phase based upon various data transmission requirements. Forexample, the isochronous transmission period may be adjusted tocorrespond to a maximum message latency. Additionally or alternatively,the isochronous transmission period may be adjusted to correspond to aratio of data per message to average data bandwidth. Thus, theprocessing system 16 may dynamically vary the isochronous phase and/orfrequency of the repeating isochronous signal to correspond to thespecific configuration of the network 10 and/or data being transmittedthrough the network 10. In some embodiments, the isochronoustransmission period is maximized to the greatest extent possible tofurther reduce power consumption.

In some embodiments, the processing system 16 may vary the isochronousfrequency to facilitate the rapid acquisition of transmitted signals andthe conservation of power. Thus, a fast isochronous frequency may beused to allow other nodes 12 to rapidly identify transmitted signals anda slower isochronous frequency may be utilized once a signal is acquiredby at least one of the other nodes 12.

The transmitted repeating isochronous signal may represent any data orinformation. Thus, in some embodiments, the transmitted repeatingisochronous signal may employ conventional message protocols andformats, such as TCP/IP and/or USB, to relay information to other nodes12. However, the network 10 and the nodes 12 may additionally oralternatively utilize the exemplary message format 24 illustrated inFIG. 3. The message format 24 may include a network address field 26, adevice address field 28, a data control field 30, a data payload field32, and a checksum field 34.

The network address field 26 allows transmission to be associated with aparticular network such as the network 10. For instance, in embodimentswhere the plurality of nodes 12 form a plurality of networks, thenetwork address field 26 allows the first node 12 a to indicate whichnetwork should utilize a particular transmitted signal. Further, in someembodiments, the first node 12 a may require other nodes to verify orauthenticate the network address associated with the network addressfield 26 before transmitting any information.

Additionally or alternatively, the nodes 12 may be adapted to receiveand/or utilize signals having network addresses corresponding to one ormore keys provided through the interface 20. For example, a receivingnode may compare data retained within the network address field 26 of anisochronous signal to a key retained within the memory 22, and utilizeor otherwise provide access to the isochronous signal only if the keymatches the data retained within the network address field 26. The keyprovided through the interface 20 and/or the data retained within thenetwork address field 26 may be encrypted to further secure the network10.

The device address field 28 may similarly allow the first node 12 a toindicate which device or devices should utilize a particular transmittedsignal. In some embodiments, the device address field 28 may be dividedinto sub-fields that represent different categories of device addressingsuch as manufacturer identification, device type, device number, deviceversion, combinations thereof, and the like. The data control field 30may be utilized for over-the-air instantaneous control functions such asmessage control and handshaking.

The data payload field 32 may be utilized to store data and informationfor use by receiving nodes and devices associated therewith. The datacorresponding to the data payload field 32 and transmitted by the firstnode 12 a may correspond to any data or information that may be used byany devices and systems. In some embodiments, the data payload field 32may be automatically seeded by information stored within the memory 22or acquired through the interface 20. For example, the first node 12 amay be configured as a window alarm sensor that automatically transmitsalarm data retained within the memory 22 when activated.

The checksum field 34 allows the integrity of the data comprising atransmitted signal to be checked by any receiving nodes. For instance,the checksum field 34 may employ a cyclical redundancy check (CRC) toensure that data corresponding to a transmitted signal is not corrupted.

In some embodiments, the first node 12 a may additionally be adapted toreceive signals, including repeating isochronous signals. For instance,the first node 12 a may be adapted to receive transmitted signals fromother nodes 12 at any time. However, in some embodiments, thetransceiver 14 utilized by the first node 12 a is configured by theprocessing system 16 to receive signals only during a guard window 36.

Thus, as shown in FIG. 4, the first node 12 a may be adapted to transmitsignals only during a transmission window 38 and receive signals onlyduring a guard window 36. Such a configuration enables the first node 12a to conserve power by only periodically transmitting or receiving.Further, as is discussed in more detail below, the guard window 36enables other nodes 12 to transmit information to the first node 12 afor use in forming a proper and non-interfering repeating isochronoussignal. For example, the first node 12 a may listen for othertransmitting nodes during the guard window 36 and variably adjust theisochronous frequency and/or isochronous phase of the repeatingisochronous signal if an interfering signal is detected.

To facilitate the detection of interfering signals, the guard window 36may be positioned in proximity in time to the transmission window 38.For example, as shown in FIG. 4, the guard window 36 may follow thetransmission window 38 to allow the first node 12 a to detecttransmissions that are likely to interfere with signals transmittedduring the transmission window 38. The guard window 36 may additionallyor alternatively precede the transmission window 38 or occur at anyother time. As is discussed in more detail below, the first node 12 amay variably adjust the isochronous phase and/or isochronous frequencyof transmitted repeating isochronous signals based on signals receivedduring the guard window 36.

The first node 12 a may also receive confirmation signals from othernodes 12 during the guard window 36 to verify that transmittedinformation was correctly received. In some embodiments, the processingsystem 16 associated with the first node 12 a may be operable to processsignals received during the guard window 36 to determine if they arepossible interfering signals or appropriate response transmissions byother nodes 12. If the signals received during the guard window 36 maycause interference, the processing system 16 may independently modifythe isochronous frequency and/or isochronous phase of the repeatingisochronous signal.

Other nodes 12 may also transmit requests to the first node 12 a duringthe guard window 36 to request that the first node 12 a change theisochronous frequency and/or isochronous phase of the repeatingisochronous signal to prevent interference with other signals. Forexample, if one of the other nodes 12, such as the second node discussedbelow, is attempting to simultaneously receive signals from the firstnode 12 a and another node 12, one or more of the nodes 12 may transmita request to the first node 12 a during the guard window 36 to preventsignal interference by requesting a change in the isochronous frequencyand/or isochronous phase employed by the first node 12 a. Thus, even ifthe first node 12 a is unaware of other interfering signals, or is notadapted to directly detect interfering signals, it may receive requestsfrom other nodes 12 to vary the isochronous frequency and/or isochronousphase of the repeating isochronous signal to limit signal interference.

By transmitting a plurality of repeating isochronous signals, the firstnode 12 a may be operable to establish a plurality of isochronouschannels. For example, a first isochronous channel may be establishedcorresponding to a first type of data for use by a first set of nodes 12and a second isochronous channel may be established corresponding to asecond type of data for use by a second set of nodes 12. The first node12 a may transmit signals corresponding to any number of isochronouschannels by appropriately defining the isochronous transmission periods,frequencies, and/or phases, for the signals corresponding to eachisochronous channel such that the transmission windows 38 for eachchannel do not overlap. The isochronous transmission periods,frequencies, and/or phases for the various channels may also be definedby the node 12 a so as to not conflict with any other device windows,such as the guard windows 36, associated with the first node 12 a.

Further, the first node 12 a may adjust the power level for therepeating isochronous signals associated with each isochronous channelto manage and control power consumption and spatially reduceinterference. Further, nodes 12 receiving transmission from the firstnode 12 a may determine their distance to the first node 12 a bymonitoring reception over varying power levels. The first node 12 a mayalso vary other characteristics of transmitted repeating isochronoussignals, such as amplitude, modulation, duration, combinations thereof,and the like, instead of, or in addition to, modifying the isochronousphase and isochronous frequency of transmitted signals.

The first node 12 a may also be adapted to transmit signals over aplurality of carrier frequencies to reduce signal interference andincrease the general bandwidth available in the network 10. In someembodiments, the first node 12 a may employ carrier frequency hoppingmethods with one or more of the isochronous channels to provide bettersystem reliability in the presence of radio interference. Although thenodes 12, including the first node 12 a, may be configured to utilizeany carrier frequency, the 2.4 GHz ISM band may be employed by variousembodiments of the present invention.

In embodiments where the network 10 includes a plurality of isochronouschannels each having an isochronous transmission period associatedtherewith, the processing systems 16 corresponding to varioustransmitting nodes 12, such as the first node 12 a, may generate eachisochronous transmission to have a different isochronous frequencyassociated therewith such that the maximum interference period betweenany two in-phase transmissions will be bounded to a maximum period thatis reasonable from an acceptable message loss point of view.

The variable selection of isochronous transmission periods, frequencies,and phases to avoid interference may further prevent inter channelinterference as discussed above and may cause all of the isochronoussignals associated with the network 10 to drift together in phase due totheir relative clock error and independently synchronize to the fastestclock source among the network channels. Such functionality causes theperiods of no wireless activity to be maximally long in the network 10,which is beneficial to the establishment of new channels in the network10.

In contrast, in embodiments where isochronous transmission periods,frequencies, and/or phases are randomly selected, the various clocksources associated with the network 10 may drift apart in phase to causea sparse channel topology and avoid synchronous interference scenarios.For example, if two nodes transmit signals having the same isochronouscharacteristics, random adjustments to the isochronous periods,frequencies, and/or phases will prevent the two nodes from remainingsynchronously locked together. Thus, the variable adjustment ofcharacteristics associated with the repeating isochronous signal may beused to create either sparse or dense channel spacing topologies andprevent interference caused by the drifting of independent channels overeach other.

In various embodiments, the network 10 may include a second node 12 boperable to receive one or more transmitted repeating isochronoussignals, such as those transmitted by the first node 12 a. Thetransceiver 14 corresponding to the second node 12 b may continuouslyreceive all broadcasted signals for storage within the memory 22 or foruse by devices and computing elements associated with the second node 12b through the interface 20.

However, to conserve power, in various embodiments the second node 12 bmay be configured to receive repeating isochronous signals according toidentified isochronous transmission periods such that constant andcontinuous signal reception is not necessary. For instance, the secondnode 12 b may receive a first repeating isochronous signal transmittedby the first node 12 a, identify the isochronous transmission period,isochronous phase, and/or isochronous frequency utilized by the firstrepeating isochronous signal, and continue to receive the firstrepeating isochronous signal based on the identified transmissioncharacteristic. Thus, by identifying one or more transmissioncharacteristics associated with a repeating isochronous signal, it isnot necessary for the second node 12 b to continuously attempt toreceive transmitted signals.

In some embodiments, the second node 12 b may first search fortransmissions by other nodes, such as the first node 12 a, to enablereception of isochronous transmissions. The second node 12 b mayautomatically search for all accessible transmissions or be adapted tosearch for transmissions only upon reception of an input, such asinformation corresponding to a received isochronous transmission and/orinformation acquired through the interface 20. In some embodiments, thesecond node 12 b may acquire transmissions by other nodes only when thesecond node 12 b first receives a signal indicating that a particularnode or isochronous channel is in a discovery state.

The second node 12 a may also chose to acquire a detected isochronoussignal based on various search criteria in addition to the discoverystate discussed above, such as by utilizing information corresponding tothe message format 24. For instance, after detecting a signal, thesecond node 12 a may acquire the signal only if the second node 12 aidentifies that the signal is transmitted by a desired device, devicetype, or other identifying characteristic, based on informationrepresented by the message format 24. For example, the second node 12 amay elect to only acquire signals that correspond to a particular typeof heart rate sensor, any heart rate sensor, or a particular heart ratesensor.

The second node 12 b may be configured to continuously search forsignals until the first isochronous transmission is identified. However,in various embodiments, as shown in FIG. 9, the second node 12 b mayselectively search for transmitted signals to conserve power. Forinstance, the processing system 16 associated with the second node 12 bmay deactivate and activate the transceiver 14 associated with thesecond node 12 b at regular or irregular periods to attempt to acquire atransmitted signal.

In embodiments where the second node 12 b is operable to receive and/ortransmit more than one signal, or participate in more than oneisochronous channel, the second node 12 b may be adapted to search fortransmissions during periods when other signals are not being receivedor transmitted such as to not interfere with established communicationchannels. For example, the processing system 16 corresponding to thesecond node 12 b may selectively activate and deactivate the transceiver14 to search for signals without interfering with the reception and/ortransmission of other signals by the second node 12 b.

In some embodiments, the processing system 16 corresponding to thesecond node 12 b may isochronously and selectively activate anddeactivate the transceiver 14 to reduce the average current draw of thesecond node 12 b and allows other isochronous signals to be receivedand/or transmitted by the second node 12 b without interference. Theduty cycle may comprise a plurality of search windows 40 spaced to beatoptimally against an expected isochronous transmission periodcorresponding to the desired signal or channel. As discussed above, thesearch windows 40 may be spaced in time such as to not interfere withthe reception and/or transmission of other signals by the second node 12b.

After identification and reception of at least a portion of atransmitted repeating isochronous signal, the processing system 16corresponding to the second node 12 b is operable to identify atransmission characteristic, such as an isochronous transmission period,frequency, or phase, corresponding to the received repeating isochronoussignal. In some embodiments, the processing system 16 may identifytransmission characteristics utilizing information represented by thereceived isochronous signal. For example, various portions of themessage format 24 may correspond to the isochronous transmission periodsuch that the processing system 16 need only process at least a portionof the received isochronous signal to identify the isochronoustransmission period corresponding to the signal. However, in otherembodiments the processing system 16 is operable to identify thetransmission characteristic independent of the data or informationrepresented by a particular signal.

In some embodiments, the isochronous transmission period or othertransmission characteristics may correspond to default values such thatthe second node 12 b may have previous knowledge of the transmissioncharacteristics, such as from information stored within the memory 22 oraccessible through the interface 20. In such embodiments, the processingsystem 16 may identify the isochronous transmission period, phase,frequency, or other transmission characteristic by accessing the memory22 or other devices and systems through the interface 20.

The processing system 16 associated with the second node 12 b may alsobe operable to identify the error in the isochronous frequency,isochronous phase, or other transmission characteristic of a receivedisochronous signal by determining a difference between an expected timeand a time at which the signal was received. As shown in FIG. 4, theprocessing system 16 may measure the time difference between an expectedreception time and an actual reception time and identify the isochronoustransmission period, phase, frequency, or other transmissioncharacteristic using the time difference. Thus, by comparing expected ordefault transmission periods with measured time differences or othervariances, the processing system 16 is operable to identify one or moretransmission characteristics corresponding to a repeating isochronoussignal.

The processing system 16 associated with the second node 12 b may alsobe operable to identify the isochronous transmission period or othertransmission characteristics by determining a difference between timesat which transmitted repeating isochronous signals are received. Forexample, the processing system 16 may identify a time at which a firstportion of a repeating isochronous signal is received, identify a timeat which a second portion of the repeating isochronous signal isreceived, and then calculate the isochronous transmission period, phase,and/or frequency based on the identified times. Thus, even when a prioriinformation regarding the transmission period is unavailable, theprocessing system 16 may still identify one or more transmissioncharacteristics.

The processing system 16 may employ any combination of the above methodsto identify the isochronous transmission period or other transmissioncharacteristics of received signals. The processing system 16 mayadditionally or alternatively employ any othercharacteristic-identifying methods to acquire the isochronoustransmission period and other transmission characteristics. For example,the processing system 16 may perform computations based on an identifiedtransmission characteristic to identify the isochronous transmissionperiod, phase, and/or frequency corresponding to a repeating isochronoussignal.

Upon identification of the isochronous transmission period or othertransmission characteristic corresponding to a received repeatingisochronous signal, the second node 12 b is operable to continue toreceive at least portions of the repeating isochronous signal accordingto the identified transmission characteristic. In various embodiments,the processing system 16 associated with the second node 12 b may beoperable to define an activation window 42 corresponding to one or moreidentified transmission characteristics to conserve node power andenable the second node 12 b to receive and/or transmit a plurality ofsignals.

As shown in FIG. 4, the activation window 42 has a duration that is atleast equal to the duration of the transmission window 38 to enable thesecond node 12 b to properly receive transmitted signals. In variousembodiments, the activation window 42 has a duration that is greaterthan the duration of the transmission window 38 to enable signals to bereceived even if the identified isochronous transmission period is offdue to miscalculation, clock error, combinations thereof, and the like.As discussed above, the processing system 16 may utilize theseidentified errors to modify the isochronous phase and/or isochronousfrequency of transmitted signals such that the signals may be receivedtowards the middle of the activation window 42. As the isochronousfrequency and/or phase is modified by the first node 12 a, the secondnode 12 b is operable to modify the activation window 42 to correspondto the modified isochronous frequency and/or phase.

In some embodiments, the activation window 42 includes error allowances,such as clock error allowances, to compensate for possible errors in theisochronous transmission period, including errors resulting from clockdrift over time between transmitting and receiving nodes. However, theactivation window 42 may be of any duration suitable for receivingtransmitted signals. As shown in FIG. 9, the activation window 42 may beutilized in combination with the search window 40 to enable the secondnode 12 b to alternatively search for and receive signals.

In some embodiments, the processing system 16 may vary the duration ofthe activation window 42 to allow other signals to be transmitted and/orreceived without interference. For example, if the second node 12 b isreceiving many signals, the activation window 42 may be dynamicallydecreased. If the second node 12 b is receiving few signals, theactivation window may be dynamically increased. In some embodiments, theprocessing system 16 may determine the duration of the activation window42 utilizing error allowances and differences between expected andactual receive times. The processing system 16 may also take intoaccount an acceptable message loss when defining or modifying theduration of the activation window 42. For example, the processing system16 may multiply the expected worst case drift per message by theacceptable number of lost messages to define the duration of theactivation window 42.

In various embodiments, the processing system 16 corresponding to thesecond node 12 b may deactivate and activate the transceiver 14 toconserve node power. For example, the processing system 16 may activatethe transceiver 14 at the start of the activation window 42 anddeactivate the transceiver at the end of the activation window 42. Thus,the identification of the isochronous transmission period, frequency,phase, and/or other transmission characteristic enables the second node12 b to conserve power through the deactivation of the transceiver 14when it is not necessary to receive signals.

The second node 12 b may receive any number of signals according to theidentified isochronous transmission period, phase, frequency, or othertransmission characteristics. Further, if a transmission characteristicis varied by the first node 12 a or other transmitting nodes 12, thesecond node 12 b may automatically identify the varied transmissioncharacteristic and continue to receive signals based on the variedtransmission characteristic.

To further conserve power, the second node 12 b may be configured tosub-sample transmissions corresponding to an isochronous channel. Thus,instead of receiving an entire repeating isochronous signal, the secondnode 12 b may elect to receive only a portion of the repeatingisochronous signal. For example, the transceiver 14 corresponding to thesecond node 12 b may be activated to receive only on every third periodof the repeating isochronous signal. Such functionality enables thesecond node 12 b to consume less energy when it is not necessary toreceive an entire signal, such as where portions of a received repeatingisochronous signal may be averaged. Further, such functionality enablessignals to be transmitted with a fast isochronous transmission period toenable rapid acquisition by the second node 12 b while allowing data tobe received by the second node 12 b at a slower rate to conserve power.

In some embodiments, the second node 12 b may be operable to transmitrepeating isochronous signals in addition to receiving repeatingisochronous signals. In various embodiments, the second node 12 b isoperable to transmit signals in a substantially similar manner to thefirst node 12 a discussed above. Thus, in some embodiments, the secondnode 12 b may transmit signals during a transmission windowcorresponding to an isochronous transmission period. The transmissionwindow may be staggered from the activation window 42 and search window40 discussed above to prevent signal interference and minimize nodepower. The second node 12 b may also be configured to transmitconfirmation signals to the first node 12 a to indicate that a signalhas been received. If the first node 12 a fails to receive theconfirmation signal, it may automatically retransmit the missing signal.As discussed above, the second node 12 b may also transmit requests tothe first node 12 a to request that a transmission characteristic, suchas isochronous frequency or isochronous phase, be modified to preventconflicts and interference between signals and channels.

In various embodiments, the first node 12 a and second node 12 b may beconfigured for relay transmissions. For example, the first node 12 a maytransmit a repeating isochronous signal, the second node 12 b mayreceive at least a portion of the repeating isochronous signal, and thesecond node 12 b may transmit at least a portion of the repeatingisochronous signal. The first node 12 a may also be configured toretransmit signals received from the second node 12 b. Thus, the variousnodes 12 may be configured as repeaters operable to repeat any receivedsignals to extend the range of the network 10.

In various embodiments, as shown in FIGS. 5 through 8, the first node 12a and second node 12 b may be configured for burst transmissions. Forexample, as shown in FIG. 5, in addition to or instead of a firstrepeating isochronous signal the first node 12 a may transmit a secondrepeating isochronous signal. Preferably the second isochronous signalhas a shorter isochronous period than the first isochronous signal. Thusthe second isochronous signal can transfer data at higher rates than thefirst isochronous signal. When the second node 12 b detects that thefirst node 12 a is burst transmitting, the second node 12 b may activelyadjust the size of its activation window 42 to ensure proper receptionof burst transmissions. For example, the second node 12 a may activelyreduce the size of its activation window 42 and associated errorallowances to account for the faster rate of burst transmissions.

The nodes 12 a, 12 b may also verify the correct burst transmission ofinformation utilizing their respective guard and/or activation windows42. For example, as shown in FIG. 5, if the first node 12 a transmits“Burst Data 1” the second node 12 b may transmit an acknowledgment“Burst Data 1A.” If an error is detected, as shown in FIG. 7, the secondnode 12 b will not transmit an acknowledge causing the first node 12 ato re-transmit the isochronous signal for reception by the second node12 b or reset the burst transmission and/or channel. The data ratesassociated with the burst transmissions may be negotiated by the firstnode 12 a and second node 12 b through bi-directional communicationbefore or during burst transmissions.

Further, in some embodiments the first node 12 a and second node 12 bmay be additionally or alternatively configured to access theirrespective memories 22 and interfaces 20 for burst transmissions. Insuch embodiments, the first node 12 a may broadcast one-half of the dataand the second-node may broadcast the other half of the data incombination to effectively double the data transmission rate withoutmodifying the respective isochronous transmission periods of the nodes12 a, 12 b.

The burst transmission discussed above may be employed in addition tothe non-burst communication methods discussed above due to the varyingisochronous transmission periods and other transmission characteristicsthat may be employed for burst channels and non-burst channels. Thus, insome embodiments, the first node 12 a, or other transmitting units, maybe operable to transmit any type of communication at every isochronousperiod and optionally receive, while the second node 12 b, or otherreceiving units, can receive or transmit any type of communication onevery isochronous period.

Upon reception of information, the second node 12 b may retransmit thereceived information as discussed above. The second node 12 b mayadditionally or alternatively retain received information within thememory 22 or provide received information to other devices and systemsthrough the interface 20. Further, the processing system 16 associatedwith the second node 12 b may process information before storage withinthe memory 22 or connection with other devices and systems through theinterface 20.

As shown in FIG. 1, the network 10 may include any number of nodes 12each configured as transmitters, receivers, or transmitters andreceivers. Thus, the network 10 may include nodes 12 configured in asimilar manner to the first node 12 a, in a similar manner to the secondnode 12 b, or in any other manner discussed herein. Several isochronoustransmission channels may be established within the network 10 withoutinterference due to the ability of the nodes 12 to vary the isochronoustransmission period or other transmission characteristics of transmittedsignals. Additional transmitting and receiving nodes 12 may be added tothe network 10 without interfering with any existing nodes 12 due to thedynamic nature of the utilized transmission characteristics. Each of thenodes 12 comprising the network 10 may independently track thetransmissions of transmitting nodes to identify utilized isochronoustransmission characteristics and properly receive signals using aminimum amount of power.

Due to the ability to vary isochronous transmission periods, phases,frequencies, and other transmission characteristics, different nodes 12within the network 10 may utilize very different transmissioncharacteristics based on the requirements of the particular transmittingnode 12. For example, a heart rate sensor may transmit data once persecond to maintain a necessary minimum data latency, while a temperaturesensor associated with the heart rate sensor may only transmit onceevery five seconds to meet a slower data latency requirement.

In embodiments where more than one node 12 attempts to transmit toanother node 12 during the same isochronous period, the transmittingnodes 12 may cooperate to avoid transmitting interfering signals. Insome embodiments, each transmitting node 12 may wait a random number ofisochronous periods before attempting to communicate with another node12 to reduce the probability of conflicting signals. Additionally oralternatively, the receiving node 12 may provide a fixed and unique subsample period to each transmitting node 12 to prevent signalinterference. The sub sample periods may be static values defined in thememory 22 or through the interface 20 or be dictated by one or moretransmitting nodes 12.

Signal interference can also be reduced by assigning a unique address toeach receiving node 12 utilizing the message format 24. The nodeaddresses may be used to produce different offsets in time from anisochronous transmission or isochronous transmission period. The nodeaddresses may be static and pre-defined values or dynamic valuesassigned by the transmitting nodes 12. Receiving nodes 12 may processthe message as the intended recipient as well as transmit anacknowledgment back to the transmitting nodes 12 at the time or offsetdefined by the message format 24. Thus, in some embodiments, the guardwindow 36 associated with transmitting nodes may be dynamicallyincreased or decreased depending on the number of receiving units. Insome embodiments, the guard window 36 may have a static durationoperable to receive acknowledgments from a fixed number of receivingunits.

Additionally or alternatively, addressing may be utilized to control howreceiving nodes respond to transmitting nodes. For example, the firstnode 12 a may transmit a repeating isochronous signal having a firstdevice address indicated by the message format 24. The second node 12 bmay receive the repeating isochronous signal and process the firstdevice address to see if it corresponds to its own address. If thedevice address identified in the message format 24 corresponds to theaddress of the second node 12 b, the second node 12 b may enable alltypes of communication methods with the first node 12 a. Consequently,nodes 12 not associated with the first device address, or other addressor identifier, will not reply during the guard window 36, thus renderingit unnecessary to utilize large-duration guard windows 36.

As discussed above, transmitting nodes such as the first node 12 a maybe configured to receive signals broadcast by other nodes 12. In someembodiments, the transmitting nodes may be operable to transmit a firstrepeating isochronous signal, as discussed above, and receive a secondrepeating isochronous signal. The processing system 16 associated with atransmitting node may estimate an isochronous frequency of the secondrepeating isochronous signal and adjust the isochronous frequency of thefirst repeating isochronous signal based on the estimated isochronousfrequency of the second repeating isochronous signal. Such aconfiguration enables interference between the first and secondrepeating isochronous signals to be avoided or limited. The processingsystem 16 may be configured to estimate the isochronous frequency of aplurality of received repeating isochronous signals, such that thepresent invention is not limited to decreasing interference between onlytwo signals.

The processing system 16 may estimate the isochronous frequency of thesecond repeating isochronous signal utilizing any of the methodsdiscussed above regarding the first node 12 a and/or second node 12 b.Thus, for example, the processing system 16 may track the secondrepeating isochronous signal over time and estimate the isochronousfrequency based on various measurements.

Thus, as is discussed above, the processing system 16 may determine adifference between an expected and actual time to identify the clockerror and then estimate the isochronous frequency of the secondrepeating isochronous signal based on the identified clock error. Theprocessing system 16 may also estimate the isochronous frequency of thesecond repeating isochronous signal utilizing only one period of thesecond repeating isochronous signal such that it is not necessary totrack the second repeating isochronous signal over an extended period oftime or access information and data represented by the second repeatingisochronous signal.

The processing system 16 may adjust the isochronous frequency of thefirst repeating isochronous signal over a plurality of transceivertransmissions so as to enable the receiving nodes 12 to continue totrack and receive the first repeating isochronous signal. Thus, for anygiven period, the instantaneous change in the isochronous frequency ofthe first repeating isochronous signal may be limited by the activationwindows 42 error allowance utilized by receiving nodes 12 to ensure thatthe first repeating isochronous signal may continue to be received.

The adjustment to the isochronous frequency of the first repeatingisochronous signal performed by the processing system 16 is variablesuch that it is not limited to static or predefined values. Thus, theprocessing system 16 may adjust the isochronous frequency of transmittedsignals by any amount to limit interference while remaining within thebounds defined by the activation windows 42 error allowance.

The processing system 16 may also be adapted to variably adjust theisochronous phase of transmitted repeating isochronous signals, such asthe first repeating isochronous signal, based on one or moretransmission characteristics of received signals, such as the secondrepeating isochronous signal or other isochronous and non-isochronoussignals. The isochronous phase adjustment performed by the processingsystem 16 may be performed in addition to, or as an alternative to, thefrequency adjustment discussed above.

The transmission characteristic utilized by the processing system 16 toadjust the isochronous phase of transmitted repeating isochronoussignals may be any characteristic that corresponds to the signal but notnecessarily the data or information represented by the signal. Thus, forexample, the processing system 16 may identify and utilize transmissioncharacteristics such as frequency, phase, power, amplitude, duration,modulation, combinations thereof, and the like. The processing system 16may adjust the isochronous phase of transmitted repeating isochronoussignals to avoid interference with other signals, to form a desiredsparse or dense network channel topology, and/or to enable receivingnodes to request a more appropriate or usable isochronous phase.

In a similar manner to the isochronous frequency adjustment discussedabove, the processing system 16 may adjust the isochronous phase oftransmitted repeating isochronous signals over a plurality oftransceiver transmissions so as to allow receiving nodes 12 to continueto track and receive the transmitted repeating isochronous signals. Forany given period, the change in the isochronous phase of a transmittedrepeating isochronous signal may be limited by the activation windows 42error allowance utilized by receiving nodes 12 to ensure thattransmitted repeating isochronous signals may continue to be received.

The adjustment to the isochronous phase of transmitted isochronoussignals performed by the processing system 16 is variable such that itis not limited to static or predefined values. Thus, the processingsystem 16 may adjust the isochronous phase of transmitted signals by anyamount to limit interference while remaining within the bounds definedby the activation windows 42. However, the interference avoidancemethods employed by the processing system 16 may include a static,measured, or random correction to the isochronous frequency, the phase,or both the isochronous frequency and phase of isochronoustransmissions.

The various nodes 12 and network 10 may be employed in any environmentto enable low-power network communications. In some embodiments, variousnodes 12 may be coupled with heart rate monitors, bicycles, speedsensors, motion sensors, pedometers, accelerometers, and the like totransmit real-time data to devices such as watches, cellular phones,personal digital assistant, computing devices, combinations thereof, andthe like. The nodes 12 may also be utilized in a home automation networkwhere alarm sensors, temperature sensors, light switches, power outlets,and the like may be controlled and monitored from a central locationsuch as a remote control or computing device. The nodes 12 may furtherbe utilized to retransmit data to a central location, such as in awarehouse of radio-frequency identification (RFID) devices, where eitherdue to distance or environment, radio-frequency communication cannot beachieved from the central location to all items in the warehouse. Thenodes 12 may also be used to allow RFID information, or any other data,to be hopped from one wireless node to another and back to the centrallocation.

The nodes 12 may be coupled with any devices and systems to form anytype of network or combination of networks. For example, the nodes 12may be utilized in combination with: computers; computer peripheralssuch as mice and keyboards; video conference equipment such as videomonitors, microphones, audio speakers, and cameras; remote controls forany devices and systems including consumer electronic products; videogame equipment such as joysticks and interactive remotes; securitysystems including security alarms, intrusion detectors, personalsecurity alarms, electronic motion detectors; electrical and heatingsystems including controllers, thermostats, heating wires; wirelessdevices such as keypads; child monitoring systems; fire and smokedetectors and alarms; personal transponders; garage door openers;combinations thereof; and the like.

It is believed that embodiments of the present invention and many of itsattendant advantages will be understood by the foregoing description,and it will be apparent that various changes may be made in the form,construction and arrangement of the components thereof without departingfrom the scope and spirit of the invention or without sacrificing all ofits material advantages. The form herein before described being merelyan explanatory embodiment thereof, it is the intention of the followingclaims to encompass and include such changes.

What is claimed is:
 1. A wireless network node comprising: a transceiveroperable to wirelessly receive a first repeating isochronous signal; anda processing system coupled with the transceiver, the processing systemoperable to selectively activate and deactivate the transceiver togenerate a duty cycle including a plurality of search windows, whereinthe search windows are spaced according to an expected isochronoustransmission period of the first repeating isochronous signal.
 2. Thenode of claim 1, wherein the processing system is further operable todetermine the expected isochronous transmission period of the firstrepeating isochronous signal.
 3. The node of claim 1, wherein thetransceiver is further operable to receive a second repeatingisochronous signal having an expected isochronous transmission period.4. The node of claim 3, wherein the processing system is operable togenerate the duty cycle based on the expected isochronous transmissionperiods of the first repeating isochronous signal and the secondrepeating isochronous signal.
 5. The node of claim 3, wherein thetransceiver is operable to receive a plurality of repeating isochronoussignals each having an expected isochronous transmission period and theprocessing system is operable to generate the duty cycle based on theexpected isochronous transmission periods of each of the receivedrepeating isochronous signals.
 6. The node of claim 1, wherein theprocessing system is operable to identify a transmission characteristicof the first repeating isochronous signal.
 7. A method of searching fora transmitted isochronous signal, the method comprising: determining anexpected isochronous transmission period of a first repeatingisochronous signal; selectively activating and deactivating atransceiver to generate a duty cycle including a plurality of searchwindows, wherein the search windows are spaced according to the expectedisochronous transmission period of the first repeating isochronoussignal; and wirelessly receiving the first repeating isochronous signalwith the transceiver.
 8. The method of claim 7, further includingreceiving a second repeating isochronous signal with the transceiver,the second repeating isochronous signal having an expected isochronoustransmission period.
 9. The method of claim 8, wherein the duty cycle isgenerated based on the expected isochronous transmission periods of thefirst repeating isochronous signal and the second repeating isochronoussignal.
 10. The method of claim 7, further including identifying atransmission characteristic of the first repeating isochronous signal.11. A wireless network comprising; a first wireless network nodeoperable to transmit a first repeating isochronous signal; and a secondwireless network node including: a transceiver operable to wirelesslyreceive the first repeating isochronous signal; and a processing systemcoupled with the transceiver, the processing system operable toselectively activate and deactivate the transceiver to generate a dutycycle including a plurality of search windows, wherein the searchwindows are spaced according to an expected isochronous transmissionperiod of the first repeating isochronous signal.
 12. The network ofclaim 11, wherein the processing system of the second wireless networknode is further operable to determine the expected isochronoustransmission period of the first repeating isochronous signal.
 13. Thenetwork of claim 11, wherein the transceiver of the second wirelessnetwork node is further operable to receive a second repeatingisochronous signal having an expected isochronous transmission period.14. The network of claim 13, wherein the processing system of the secondwireless network node is operable to generate the duty cycle based onthe expected isochronous transmission periods of the first repeatingisochronous signal and the second repeating isochronous signal.
 15. Thenetwork of claim 11, wherein the processing system of the secondwireless network node is operable to identify a transmissioncharacteristic of the first repeating isochronous signal.
 16. Thenetwork of claim 11, wherein the transceiver of the second wirelessnetwork node is operable to receive a plurality of repeating isochronoussignals from a plurality of other network nodes, each received repeatingisochronous signal having an expected isochronous transmission period,wherein the processing system of the second wireless network node isoperable to generate the duty cycle based on the expected isochronoustransmission periods of each of the received repeating isochronoussignals.